GEOLOGICAL RELATIONS. 



17 



published in the Maine reports. The resemblances to Huronian schists 

 may show the origin of the materials, and, necessarily, the later age of 

 the fossiliferoiis beds. 



One of the most characteristic formations of the East is the Gaspe 

 slate group, including the calciferous mica schist of Vermont, and the 

 Coos group of New Hampshire. Commencing at the Gulf St. Lawrence, 

 there is a broad band of slates, slaty grits, with calcareous, ferruginous, 

 and sandy varieties, often carrying Lower Helderberg, and perhaps 

 Niagara fossils. They are several thousand feet thick. Little is yet 

 known of them, save their general distribution. They extend south- 

 westerly through Quebec, New Brunswick, and Maine, entering Vermont 

 and New Hampshire with a somewhat altered facies. Logan describes 

 them on all the north-west-south-east streams tributary to the St. Law- 

 rence. The area of its distribution is mostly in a forest. In northern 

 Maine I have crossed it along the St. John's river, as high as the mouth of 

 the Alleguash. The divisional planes are commonly nearly vertical, con- 

 sisting in so many places of cleavage that one is tempted to believe the 

 strata lines are mostly obliterated. No formation occupies a larger area 

 upon our map than this. 



In Quebec, as we approach the United States boundary, two types of 

 rock prevail in the Gaspe series, — one, a well defined clay slate, abundantly 

 quarried for tiles, traversed by cleavage planes, and a siliceous limestone. 

 The slates contract near the line. A narrow area passes from Mem- 

 phremagog lake, through Montpelier, to a point beyond the centre of 

 Vermont. Another enters New Hampshire in Pittsburg, crops out at 

 intervals along the Connecticut valley, being quite prominent between 

 Bellows Falls and Greenfield, Mass. The limestone seems to undergo a 

 species of metamorphism, as it passes from north to south. For fifty 

 miles of its course in Quebec it is clearly a limestone. As it passes into 

 Vermont, micaceous and hornblendic layers show themselves, and in- 

 crease southerly, so that midway in Vermont the schists and calcareous 

 layers are equal in amount. It is here, also, that the area contracts very 

 much. In southern Vermont and in Massachusetts the mica schists pre- 

 dominate, and the limestones are scarce. The formation terminates near 

 the north line of Connecticut, but appears in a limited area, west of the 

 Huronian and clay-slate outcrops, near New Haven, Conn. 



VOL. II. 3 



